Modulating Aggregation in Microemulsions: The Dispersion by Competitive Interaction Model

A phenomenological model has been developed for the mechanism of action of phase modifiers as additives that control aggregation phenomena within water-in-oil emulsions. Unlike the qualitative “cosolvent” and “cosurfactant” paradigms previously discussed in the literature, the new “Dispersion by Competitive Interaction” model (DCI) explicitly considers the strength and prevalence of different intermolecular interactions that may compete (or act cooperatively) to influence aggregate dispersion and influence phase phenomena within microemulsions. The prior cosolvent and cosurfactant models are considered distinct “regimes” within DCI where either self- or cross-interactions dominate within the landscape of intermolecular interactions. The specific system under consideration, the N,N,N\textsuperscript{$'$},N{$'$}‐tetraoctyl diglycolamide amphiphile extractants with tributyl phosphate or dihexyl octanamide phase modifier additives, represents a new regime – labelled the polar disruption regime – where the phase modifier interactions with the polar micellar core (cross-interactions between different components) are strong enough to disrupt the self-interactions of polar-solute molecules amongst themselves.